Process of purifying water.



C. P. HOOVER.

PROCESS 0F PURIFYING WATER.

lAPPLICATION FILED JULY l1. 1916.

t f y Patented Sept. 5, 1916.

2 SHEETS-SHEET 1.

.C. P. HOOVER.

Paocess or PURIFYING WATER.

APPLICATION FILED JULY I1, 1916. L 791 93 PatentedSept. 5,1916.

2 SHEETS-SHEET 2.

` CHARLES PaHOOVER, OlE COLUMBUS, OHIO.

PROCESS 0F PURIFYING WATER.

mamas..

Specification of Letters Patent.

Patented Sept. 5, 1916,

Continuation of application Serial No. 870,891, led November 7, 1914'. This application led July 11, 1916.

. Serial No. 108,596.

Toall whom t may concern:

Be it known that l, CHARLES P. HOOVER, a citizen'of the United States, residing at Columbus, in the county of Franklin and State of Uhio, have invented certain new and useful Improvements. in Processes of Purifying Water, of which the following is a specification.

` This invention relates to processes of purifying water; and it comprises a process wherein bauxite, halloysite or other native hydrated aluminous material containing aluniinal is treated with sulfuric acid and the resultant material comprising the sulfuric acid'soluble and sulfuric acid insoluble constituents is added to the water to be purified, advantageously after a Fdilution with a certain amount of water, with the result of forming a gelatinous coagulating precipitant containing aluminum hydroxid, A1,(0H3), which has as a nucleus the sulfuric acid insoluble constituents of the native ore; all as more fully hereinafter set forth and as claimed.

1t has been ,customary in treating water, to use what is commonly known as alum cake This alum cake is aluminum sulfate and is made from bauxite by digesting it with sulfuric acid in a lead lined tank, allowing the mixture to settle usually for a day or two, withdrawing the supernatant liquid containing the. sulfuric acidv soluble constituents of the bauxite, filtering out any -tially chemically neutral solution; that is y water, it is known that the more basic the suspended matters, evaporating the filtered solution, and crystallizing the resultant product. The relative amounts of acid and of alumina are such as to give a substana solution containing sulfuric acid and alumina in the ratio 3S032-A1203.

` linthe use of alum cakein purifying' material, lthe better it works; that is, the' larger the ratio of Al203:S03,'the better is its operation in purifying water. This is for a number of reasons.` The'alumina, A120, is the active agent and the .sulfuric acid is, so to speak, merely asolvent. Butl it is difficult in a commercial way to make an alum cake which is much more baslc neutral alums.

of the basic sulfates, the difiiculty of procuring a clean crystalline product readily redissolving in water to a clear solution, etc.' lt is substantially impossible in the usual processes of dissolving, settling, filtering, or

otherwise clarifying and evaporating, to have any substantial excess of alumina over the amount necessary for the neutral sul- K fate (AlSQS) accompany the material forward; this being true not only of alumina which has not combined with the acid but also of alumina combining with acid to form the less soluble or insoluble sulfates. lin the case of these latter compounds in so far as they go into solution during digestion, on dilution the basic alumina is apt to hydrolyze quickly, become insoluble and be lost with the insoluble residue remaining after digestion; a residue which is always discarded in making the commercial sulfate. But, as stated, the more basic alums are better than the neutral salt. With them, the flocks or coagulants form more rapidly and are much larger than is the case with This is true with clear hard water, with a soft water moderately clear, and with a highly colored water. In lcommercial use, the specifications for filter alum in this country now substantially universally require that it shall be somewhat basic; that it shall contain several per cent. of alumina in excess of the vamount theoretically' necessary to combine with the sulfuric acid present to form the chemically neutral aluminum sulfate.

As stated, the function of the sulfuric acid is really only that of a solvent; it Ais something to get the alumina into solution and when the material is added to thev water to be purified in the liquid form, itl is kexpected that thel carbonate of lime in the sary to be added, more base must be, andis, supplied as soda orlime.

Water purification are concerned, the less sulfuric acid there is present, that is the '-more basicthe alumina sulfate is, the bet- .l ter.I The sulfuric acid in the large amount A usedin' the ordinary process of manufacture is a'necessary evil; there must be a relatively large amount of sulfuric acid present inorder to make the filter alum or sulfate of I' of in water purification and producing a much better type of clarification.

In the old process of making filter alum from bauxite, as stated, it was the effort to use theoretically combining proportions of alumina and of sulfuric acid with perhaps a little excess of alumina so as to make the sulfatepof alumina as basic as the process would stand for. In so doing the extra base over and above that which went into solution separated asa sludge, together with a certain amount of the sulfuric acid used and carried down as a basic salt together -With the acid insoluble materials. This sludge was discarded. This Wasted sludge contained n ot only alumina and sulfuric acid, so that its production was a sourceof loss, but it also contained some iron oxid, hydrated silica, aluminum silicate (clay), silica, titanium oxid, etc. But I find this sludge is itself a useful adjunct to the sulfate of alumina in water clarification; and so much so that I ordinarily purposely add to its amount by cutting down the amount of acid somewhat.4 The reduction in the amount of acid not only gives me a more basic material which is desirable, but also v gives me more sludge.

My invention is relatively simple and inv expensive as compared with the heretofore known processes of clarifying water with the filter alum above described, andit results in the possibility of use of a comparatively greater per cent. of basic alumini, as

well as of the silica and silicates, iion, alumina and titanium oxids and other materials useful for coagulatingand clarifying water, all of which I termsu'lfuric acid insoluble constituents of thena'tive hydrated material used. And there no waste of` sulfuric acid; but, on the other hand, all the sulfuric acid which I use is utilized and I am enabled to employ the minimum necessary for the present purposes.

According to my invention, I treat bauxite with sulfuric acid and then add the resultant product directly to the Water without sedimentation or'liltration.. `Ordinarily It is' evident, therefore, that so far as the demands of' I -iemploy considerably less sulfuric acid than is chemically equivalent to the alumina and other bases present. For example, for

T100 parts by weight of bauxite containing 52 parts of available or acid soluble alumina,

may use 139 parts by weight of ordinary 66 sulfuric acid. The sulfuric acid may be diluted with 1 to 70 parts of water, the bauxite added and the mixture stirred without external heating until reaction appears to be complete. The product obtained contains undecomposed bauxite, the oxids above mentioned, and basic alumina, (all of which are lost in theprocesses heretofore known) in addition to the neutral and basic sulfatesV `of alumina in solution. This material is quite basic;l it contains a higher percentage of dissolved alumina in proportion to the sulfuric acid than can be obtained from a material which has been reduced to dryness upon subsequent treatment with water. The whole material thus produced is used for treating Water and in this treatment the presence of the undecomposed bauxite and other insoluble matters serve as a matrix to start the coagulation. The presence of the high percentage of basic alumina hastens the coagulation. It has coagulative pro erties in and of itself, that is, it does not epend as does the neutral sulfate, upon the action of bases to form' coagula, and it causes the flocks to be larger.

In the accompanying drawing I have shown more or less diagrammatically apparatus capable of performing my process.

. Figure 1 is a diagrammatic illustration, partly in elevation and partly in section of one form of apparatus; and Fig. 2 is a similar view of a slightly modified form.

In the drawings, 1 indicates an elevator, 2 a Weighing hopper, 3 an acid measuring tank, 4 a lead-lined boiling tank, 5 an alum measuring tank in communication with the lead tank by means of pipe 6, 7 a pipe leading from the alum tank to the chemical solution tank 8, 9 a feed pipe leading to the chemical feed regulator 10, 11 a pipe leading to the water main 12, 13 a mixing tank through which the Water and the solution flow, 14 a water overflow from the mixing tank, 15a sedimentation basin, 16 the overflow or pump suction and 17 a sludge drain. I may use agitator 25in tank 4; under certain conditions on shaft 26 operated by pulley 2'7.

In Fig. 2 the same reference characters designate parts corresponding to those of Fig. 1. However, in this view the tank 5 is provided with stirrer 18 operated through bevel gears 19 on shaft 20 provided with pulley 2l, and this tank 5 may have the outlet or plug valve 22 feeding mater1al 1nto a solidifying pit 23 wherethe material remains for `a short while yand solidifies. f

ile in this pit 23 water is evaporated od' by the heat of reaction between' sulfuric acid and water and the material may become solid vbut it is noted that su'ch solid material contains everything but the water originally present; there is no elimination of any ofthe impurities. In other words no l From this stage the apparatus used is similar to that in Fig. 1.

lf may use either the apparatus of Fig. 1 or of Fig. 2. Y'

Referring to the drawings, and particularly Fig. 1, finely pulverized bauxite is carrid by elevator 1 into weighing hopper 2 and sulfuric acid is measured in tank 3 and discharged into the lead-lined boiling tank 4. Water is then added and the heat of reaction between the water, and acid causes the mixture to become hot. l may however use heatingv means for tank 4 if desired. Pulverized bauxite is fed slowly fromvthe weighing hopper 2 into the hot acid solution and the reaction is allowed to continue from 3 to 4 hours, usually without any external'heat. Subsequently itis usually necessary to boil the solution in tank 4 by means of steam coils or live steam for several hours longer to complete .the reaction to the desired extent. After this boiling process is completed the tank 4 is filled with water and A'the mixture is thoroughly agitated by means of air or paddles. After the mixture is thoroughly agitated a portion is discharged through pipe 6 into measuring tank 5, and then ejected through pipe 7 into chemical solution tank 8. ln tank 8 the mixture is further diluted and it is discharged by pipe 9'. into a chemical feed regulator of any ordinary type whence it passes by pipe 11 tothe water main 12. The water thus treated is caused to circulate through the mixing tank 13 where coagulation takes place and is discharged through water overflow 14 toy sedimentation basin 15 where it is allowed to settle;

-tation basin 15, is discharged through the sludge drain 17. l

The apparatus of Fig. 2 dijders slightly from that of Fig. 1. The bauxite and acid ,l are stirred together in tank 4 by means .of the plates 18 operated through the gears 19,.

shaft 20 and pulley 21. Afterv being mixed 'llhe clear water is drawn od from the pump suction or' overflow 16 while the for about 5 or 10 minutes the mixture is dis-A charged through the plug valve 22 inte.

solidifyingtray or pit 23. lin this solidi- J fying pit the mixture boils violently and on cooling forms a hard cake, which cake contains all the original constituents. YI'Fhe xcake' is dug from the pit 23 and a part is dissolved and disintegrated indissolving tank 24, and then ejected through pipe 7" into chemical solution tank 8, where it is diluted with water and used in exactly the same manne'r as in the process just described.

- Among the advantages of my process are "itt the following: llt uses the sludge or insoluble material of the alum syrup as well as what may be termed the semi-soluble or basic material as well as the normal Yor neutral sulfate. ln heretofore known processes part of the available alumina and particularly the-\ basic alumina is lost.' ltn my process all of the alumina content is effective andl utilized. ln my process lf do not try to separate the alumina sulfate from the undissolved material but allowall this material to remain in suspension and use both it and the normal sulfate formed in the action. Further l lose absolutely none of the alumina.

A further advantage of my process is that l produce and use highly basic forms of alumina sulfate and such compounds are less stable than the firmly combined alumina ofthe normal sulfate and consequently disdit associate very quickly. This is a decided advantage because in thetreatment of water substantially neutral solution, that is, a soin-' tion containing sulfuric acid and alumina in the ratio of 3SO3:A12O3. As stated, in my process ll can use 52 parts of available or acid soluble alumina tqas low as 139 parts of 66 sulfuric acid.

When th'e mixture is added to a hard water, the sulfuric acid present combines with the lime and magnesia of the water, setting free alumina in gelatinous form. 'll'lie' sludge or residue of the material allttltl lllf lldt

ready contains some gelatinous alumina.:

The Whole insoluble materials of ythe mix,` that is, those materials which were not af-v fected by the sulfuric acid, the semi-converted insoluble materials and the gelatinous alumina already present, as well as thatd formed by the interaction of the neutral and basic sulfates of alumina of the solution with the basic bodies of thev water, all cooperate in producing a highly efficient clarification; and this clarification is effected, as

it is found, with considerable less material e impurities of the water in forming nuclei Nov.

for the separation of the gelatinous alumina, not only that produced by the interaction of the constituents of the water but that already present and assist informing larger, better settling coagulaand flocks with a resultant better separation of the mud and dirt in the water. This assistance is particularly useful in the case of rather clear waters containing very little insoluble material adapted to act in'this nucleus manner. t

This application is a continuationA of my prior application, Serial No. 870,891, filed What I claim is 1. The process of treating water which V comprises mixing sulfuric acid and native soluble constituents of hydrated aluminous material to form a composition comprising aluminum sulfates and sulfuric acid-insoluble constituents of the material, adding such composition directly to the water to be purified and thereby .forming aluminum hydrate, settling such aluminumhydrate together with entrapped impurities and the initial sulfuric acid-insoluble constituents, and drawing off the purified water for use. n

2. The process of treating water which comprises mixing sulfuric acid and bauxite to form a composition comprising aluminum sulfate and sulfuric acid insoluble constituents of bauxite, adding such composition directly to the water to be purified and thereby forming aluminum hydrate, settling such aluminum hydrate together with entrapped impurities and the initial sulfuric acid insoluble constituents, and drawing off the purified water for use.

3. The process of purifying water which comprises treating native hydrate aluminous material with sulfuric` acid in quantity sufficient to make a composition containing basic sulfates andI sulfuric acid insoluble constituents of the material, adding such composition to the water to be purified, thereby forming aluminum hydrate, settling such aluminum hydrate together with entrapped impurities and the sulfuric acid in- I the original material, and drawing off the purified water for use.

ll. The process of purifying water which comprises treating native hydrated alumimaterial, allowing the material -to form coagulants comprising aluminum hydrate and the said `sulfuric acid insoluble constituents of the native material, settling the said coagulants, and drawing ofil the purified water for use.

6. The process of purifying water which comprises treating native hydrated aluminous material with sulfuric acid to form a substance containing aluminum sulfates and.

sulfuric acid-insoluble constituents'of the material, allowing the substance to solidify, adding water to a portion of the substance to form a magma containing sulfuric acid soluble and sulfuric acid insoluble constituents of the native material, adding the magma thus formed to the water to be purified, settling the aluminum hydrate formed together with entrapped impurities and the sulfuric acid insoluble constituents of the magma, and drawing off the puried water for use.

7. The process of purifying water which comprises treating bauxite with sulfuric acid and water to form a substance containing aluminum sulfates and sulfuric acid insoluble constituents of bauxite, allowing the substance thus formed to solidify, adding Water to a portion of the substance to form a magma containing sulfuric acid soluble and sulfuric acid insoluble constituents of the bauxite, adding the magma thus formed to the water td be purified, settling the aluminum hydrate formed together with the entrapped impurities and the sulfuric acid insoluble constituents of the magma and drawing ofi' the purified water for use.

8. In the purication of water the process which comprises adding thereto a magma containing the sulfuric acid soluble and the sulfuric acid insoluble constituents of native hydrated aluminous material.

9. In the purification of water the process which'comprises adding thereto a magma containing the sulfuric acid soluble and sulnative aluminous material together With certain sulfuric acid insoluble constituents of the native aluminous material consisting of titanium oXid, iron oXid, clay and sand.

11. 'The process of purifying Water which comprises adding thereto a magma containing the sulfuric acid soluble constituents of bauxite together With a mixture of sulfuric acid insoluble constituents comprising ti.

, CHARLES P. HOOVER. 

